Vulnerability refers to characteristics or situations that make people, places, systems, or assets susceptible to the damaging effects of hazards. The document defines vulnerability and categorizes it into four main types: physical, social, economic, and environmental vulnerability. Examples are provided for each type to illustrate factors that increase susceptibility to hazards like earthquakes, floods, pandemics, and more. Reducing vulnerability requires understanding its drivers and taking steps to address factors within each category like improving building construction, assisting vulnerable groups, stimulating livelihoods, and better environmental management.